Semiconductor manufacturing apparatus including temperature control mechanism

ABSTRACT

A semiconductor manufacturing apparatus includes a furnace having a tubular body with inner and outer tubular members. A boat having wafers mounted thereon is positioned inside the inner tubular member. Temperature control inside the tubular body is provided by a thermocouple device located between the inner and outer tubular members. A mixture of dichlorosilane gas and ammonium gas formed by a mixing nozzle at a temperature which is lower than the temperature in the tubular body is supplied to the wafers from positions juxtaposed with the wafers mounted on the boat.

.Iadd.This application is a continuation of application Ser. No.08/088,525, filed Jul. 9, 1993, now abandoned, which is a Reissueapplication Ser. No. 07/330,044, filed Mar. 29, 1989, now U.S. Pat. No.5,029,554. .Iaddend.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an improved semiconductor manufacturingapparatus comprising a LP-CVD (Low Pressure CVD) device.

2. Description of the Related Art

FIGS. 1 and 2 of the accompanying drawings respectively schematicallyillustrate a horizontal type LP-CVD device and a vertical type LP-CVDdevice of the prior art. In FIG. 1, the horizontal type LP-CVD devicecomprises a heater 1, a chlorosilane gas nozzle 2, an ammonium gasnozzle 3, a reaction tube 4, an emission port 5 and wafers 6. On theother hand, the vertical type LP-CVD device shown in FIG. 2 comprises anouter tube 7, an inner tube 8, a furnace port flange 9, wafers 10, adichlorosilane gas nozzle 12, an ammonium gas nozzle 13 and a heater 14.

When silicon nitride films are manufactured in an apparatus as shown inFIG. 1 or 2, the inside of the reaction tube 4 or the outer tube 7 ismaintained at a low pressure between 20 and 50 (Pa) and dichlorosilanegas and ammonium gas are respectively supplied through the gas nozzles 2and 3 in FIG. 1 or the nozzles 12 and 3 in FIG. 2 so that films areformed on the wafers 6 of FIG. 1 or the wafers 10 of FIG. 2 in thefurnace (having the reaction tube and the heater) which has atemperature gradient between 770° C. and 790° C. realized by the heater1 of FIG. 1 or the heater 14 of FIG. 2. It should be noted that thefurnace port 4₁ and the pump 42 (or the emission port 5) respectivelyconstitute the lower and higher ends of the temperature gradient in FIG.1, while the furnace port 7₁ and the furnace bottom 7₂ respectivelyconstitute the lower and the higher ends of the temperature gradient inFIG. 2.

In FIG. 1, the reaction tube 4 is surrounded by the heater 1. Thedichlorosilane gas nozzle 2 and the ammonium gas nozzle 3 respectivelysupply dichlorosilane gas and ammonium gas so that films are formed onthe wafers 6 respectively. For formation of films, the gaseous reactionproduct is emitted from the emission port 5. Similarly in FIG. 2, theouter tube 7 is surrounded by the heater 14. Dichlorosilane gas andammonium gas are respectively supplied from the dichlorosilane gasnozzle 12 and the ammonium gas nozzle 13 to form films on the wafers 10.The gaseous reaction product is emitted from the emission port 11located outside of the inner tube 8. Boat 15 is moved in or out byraising or lowering the furnace port flange 9 by an elevator.

In short, with a horizontal type LP-CVD device or a vertical type LF-CVDdevice of the prior art, silicon nitride films are formed in anenvironment where a temperature gradient is present as described above.More specifically, U.S. Pat. No. 4,279,947 issued to Goldman et al.discloses an apparatus wherein a plurality of substrates are arranged ina reaction tube and dichlorosilane gas and ammonium gas are flowed andbrought to react on the substrates in a vacuum condition betweenapproximately 300 millitorr and 20 Torr and at temperature ofapproximately 650° to 800° C., a temperature gradient of approximately100° C. being realized along the gas flow.

Such a temperature gradient is required in an apparatus of the prior artto ensure an even thickness of the silicon nitride film product. If thefilm deposition process is conducted in a furnace where no temperaturegradient is present, or under a temperature flat condition, the filmsproduced near the furnace port will have a thickness which is greaterthan that of the films produced near the furnace bottom so that filmswith different thicknesses will be obtained as final products. In short,the temperature gradient is designed to offset the variation ofthickness.

However, the provision of a temperature gradient in the furnace hascertain drawbacks. First the etching speed of the silicon nitride filmis inevitably dependent on the growth temperature of the film. Thehigher the growth temperature, and therefore the growth speed of thefilm, the lower the etching speed becomes.

Second the (expansion or contraction) stress of the silicon nitride filmis also dependent on the growth temperature, so that the higher thegrowth temperatures, the smaller the stress. Therefore, films formed ina furnace having a temperature gradient have qualities which varydepending on where the wafers are arranged on the same boat.

SUMMARY OF THE INVENTION

It is therefore the object of the invention to provide a semiconductormanufacturing apparatus that can produce silicon nitride films having anidentical thickness and identical qualities in the same charge lot.

The above object of the invention is achieved by providing asemiconductor manufacturing apparatus of the vertical LP-CVD typecomprising furnace means having tubular body and heating means arrangedaround the circumference of the tube body; boat means removablyaccommodated in the tube body of the furnace means and provided withwafers for formation of films; temperature control means arranged in thefurnace means for maintaining evenness of the temperature and providinga temperature flat area in said furnace means; mixed gas supply meansfor supplying a mixture of dichlorosilane gas and ammonium gas mixed ina temperature range lower than the temperature range of said temperatureflat area into the tube body in the direction from the wafer locatednearest to the bottom of the tubular body toward the wafer locatednearest to its entrance; and gas supplying means for separatelysupplying dichlorosilane gas and ammonium gas from said boat means inthe direction from the wafer located nearest to the inlet of the tubebody toward the wafer located nearest to its bottom.

The semiconductor manufacturing apparatus according to this invention iscapable of providing an even and identical temperature throughout theinside of the furnace and hence a temperature flat area there so thathomogeneous films are formed on the wafers in the furnace after anetching treatment. The apparatus according to this invention is freefrom any trouble caused by a clogged nozzle which takes place with anLP-CVD device of the prior art where only dichlorosilane gas is suppliedtherethrough, since a mixture of dichlorosilane gas and ammonium gas issupplied through the nozzles of the apparatus at a temperature rangelower than that of the temperature flat area to the wafers in thefurnace.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view illustrating a semiconductormanufacturing, apparatus constituting a horizontal LP-CVD device of theprior art;

FIG. 2 is a schematic sectional view illustrating a semiconductormanufacturing apparatus comprising a vertical LP-CVD device of the priorart;

FIG. 3 is a schematic sectional view illustrating an embodiment of thesemiconductor manufacturing apparatus according to the invention;

FIGS. 4A and 4B are, respectively, a plan view and a side viewillustrating a mixed gas nozzle of the embodiment of FIG. 3;

FIG. 5 is a graphic illustration showing the relationship between thefilm thickness and the position of the wafers in the furnace of thepresent invention and that of the prior art for comparison to evidencethe evenness of the thickness of the films produced by the presentinvention;

FIG. 6 is a graphic illustration showing the relationship between thevariation of thickness and the position of the wafers in the furnace ofthe present invention and that of the prior art.

FIG. 7 is a table comparing the performance device of the a horizontaltype LP-CVD device of prior art in terms of the thickness of filmsformed in the presence of a temperature gradient and that of a verticaltype LP-CVD device according to the invention in terms of the thicknessof films formed in a temperature flat area; and

FIG. 8 is a semiconductor manufacturing apparatus comprising ahorizontal LP-CVD according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Now the present invention will be described in greater detail byreferring to a preferred embodiment illustrated in FIGS. 3 through 8.

.Iadd.The furnace employed in the apparatus shown in FIGS. 3-8 isgenerally referred to as a hot wall type. .Iaddend.

As shown in FIG. 3, a semiconductor manufacturing apparatus having avertical type LP-CVD device according, to the invention comprises afurnace. The furnace includes an outer tubular member 7, an innertubular member 8 and a heater 14 provided around the periphery of theouter tubular member 7.

A boat 15 having wafers 10 mounted thereon is accommodated in the innertubular member 8 and supported by a furnace port flange 9 so that theboat 15 can be moved into and out of the furnace by raising and loweringthe furnace port flange 9 by an elevator not shown in the drawing.

A thermocouple cover 24 is provided between said inner tubular member 8and the outer tubular member 7 for controlling the temperature in thefurnace. A heat screening plate 25 is provided between the flange 9 andthe boat 15. A nozzle 12 for supplying dichlorosilane gas and a nozzle13 for supplying ammonium gas into the furnace are arranged at thefurnace port. A mixing gas nozzle 21 is provided along the longitudinaldirection of the boat 15 for supplying a mixture of dichlorosilane gasand ammonium gas to the wafers located near the bottom of said innertube 8. Reference numeral 23 in FIG. 3 denotes a gas nozzle for blowingnitrogen gas. According to the present invention, the gas mixingoperation is conducted at a low temperature range and the temperature inthe furnace is evenly maintained and at a constant level. Thermocouplesin the thermocouple cover 24 measure the temperature in the furnace atfour predetermined points and control the temperature so that atemperature flat condition is maintained in the furnace. FIG. 4A is aplan view of the mixing gas nozzle 21 and FIG. 4B is a side viewthereof. Dichlorosilane gas is supplied from gas port . .211.!..Iadd.21₁ .Iaddend.and ammonium gas is supplied from gas, port . .212.!..Iadd.21₂ .Iaddend., which are then mixed in the mixing gas nozzle 21 sothat the mixed gas is blown out of holes 22. The holes 22 are arrangedwithin the upper half of mixing gas nozzle tube 21, which is juxtaposedwith the upper flat of the boat.

It should be noted that the gas ports . .211.!. .Iadd.21₁ .Iaddend.and ..212.!. .Iadd.21₂ .Iaddend.are located near the furnace port flange 9and operate at a low temperature within the temperature range between30° and 180° C. for mixing with a view to prevent clogged nozzles fromtaking place by suppressing pyrolysis of dichlorosilane gas as the gasmixing operation is conducted at a low temperature within the rangeindicated above.

For the purpose of comparison, silicon nitride films were formed byusing a vertical type LP-CVD device as shown in FIG. 3, where atemperature gradient was maintained in the furnace and dichlorosilanegas and ammonium gas were respectively supplied from the dichlorosilanegas nozzle 12, the ammonium gas nozzle 13 and the mixing gas nozzle 21simultaneously for reaction.

FIGS. 5 and 6 show the degree of evenness of the films formed by avertical type LP-CVD device of the prior art (FIG. 2) and that of thefilms produced by a vertical type LP-CVD device according to theinvention (FIG. 3). In these graphic illustrations, dotted line Arepresents the films formed by a vertical type LP-CVD device of theprior art having no temperature gradient and dotted line B representsthe films formed by a vertical type LP-CVD device of the presentinvention having no temperature gradient. It is obvious from thesegraphic illustrations that silicon nitride films having a nearlyidentical thickness are formed by an apparatus comprising a verticalLP-CVD device according to the invention.

FIG. 7 is a table showing the degree of evenness of thickness of thesilicon, nitride film produced by a horizontal type LP-CVD device of theprior art (FIG. 1) and those produced by a vertical type LP-CVD deviceof the invention. From the table of FIG. 7, it is obvious that avertical type LP-CVD device of the invention can produce silicon nitridefilms having a thickness which is almost identical to the horizontaltype LP-CVD device of the prior art having a temperature gradient. Itshould be noted that FIG. 7 shows dispersions of thickness of the filmsprepared by an apparatus charged with 100 five-inch wafers. Theconditions of film depositon for a vertical type LP-CVD device of theinvention are as follows: growth temperature: 780° C. flat, growthpressure: 0.15 Torr, dichlorosilane gas flow rate: 90 cc/min, ammoniumgas flow rate: 450 cc/min. The conditions for a horizontal type LP-CVDof the prior art are as follows: growth temperature: 770°-780°-790° C.,growth pressure: 0.35 Torr, dichlorosilane gas flow rate: 37 cc/min,ammonium gas flow rate 160 cc/min.

FIG. 8 shows another embodiment of the present invention comprising ahorizontal type LP-CVD device. As in the case of the above embodiment,this embodiment differs from a horizontal type LP-CVD device of theprior art (FIG. 1) in that it comprises a mixing gas nozzle 21 andreactions are conducted under a temperature flat condition in thefurnace. The rest of the reaction conditions as well as the effects ofthis embodiment are similar to those of the above described embodiment.

It will be obvious that various alterations and modifications can bemade to the above embodiments within the scope of the present invention.For example, while dichlorosilane gas and ammonium gas are introducedseparately into the furnace in the above embodiments, they can beintroduced after having been mixed with each other. It should also benoted that the ratio of the flow rate of dichlorosilane gas and that ofammonium gas is advantageously found between 1:5 and 1:15.

What is claimed is:
 1. A semiconductor manufacturing apparatuscomprising:furnace means including heating means and a tubular bodycomprising an inner tubular member and an outer tubular member, thetubular body having an inlet region at a first end of the tubular body,and a furnace port flange connected to the tubular body at a second endof the tubular body, and the heating means being provided around theperiphery of the outer tubular member; boat means removably inserted inthe tubular body; a plurality of wafers provided on the boat means eachhaving a thin film formed thereon; temperature control means provided inthe tubular body between the inner tubular member and the outer tubularmember for controlling the temperature therein, to maintain thecircumference of the boat means at a uniform temperature; mixed gassupply means provided in the furnace means for supplying a mixture ofdichlorosilane gas and ammonium gas, mixed at a temperature lower thanthe uniform temperature in the tubular body, into the tubular bodyadjacent wafers disposed nearest the inlet region of the tubular body;and gas supply means for separately supplying dichlorosilane gas andammonium gas into the tubular body adjacent wafers disposed nearest thefurnace port flange.
 2. A semiconductor manufacturing apparatusaccording to claim 1, wherein the ratio of the flow rate ofdichlorosilane gas and that of ammonium gas for producing mixed gas isbetween 1:5 and 1:15.
 3. The semiconductor manufacturing apparatusaccording to claim 1, wherein the temperature for mixing dichlorosilaneand ammonium gas is about 30° to about 180° C.
 4. A semiconductormanufacturing apparatus comprising:furnace means including heating meansand a tubular body having an inner tubular member and an outer tubularmember, the tubular body having a furnace port flange connected to oneend of the tubular body, and the heating means being provided around theouter periphery of the outer tubular member; boat means removablyinserted in the tubular body; a plurality of wafers provided on the boatmeans each having a thin film formed thereon; temperature control meansprovided in the tubular body between the inner tubular member and theouter tubular member for controlling the temperature therein to maintainat least a portion of the tubular body at a uniform temperature; mixedgas supply means provided in the furnace means for supplying a mixtureof dichlorosilane gas and ammonium gas, mixed at a temperature lowerthan the uniform temperature in the tubular body, into the tubular bodyadjacent wafers disposed nearest the inlet region of the tubular body.5. A semiconductor manufacturing means according to claim 4 wherein theratio of the flow rate of dichlorosilane gas and that of ammonium gasfor producing mixed gas is between 1:5 and 1:15.
 6. The semiconductormanufacturing apparatus according to claim 4, wherein the temperaturefor mixing the dichlorosilane gas and the ammonium gas is between about30° and about 180° C.
 7. The semiconductor manufacturing apparatus ofclaim 4, further comprising gas supply means for separately supplyingdichlorosilane gas and ammonium gas into the tubular body adjacentwafers disposed nearest the furnace port flange. .Iadd.
 8. Asemiconductor manufacturing apparatus comprising:hot wall furnace meansincluding heating means for producing a first temperature region and asecond temperature region inside the furnace means, the secondtemperature region being lower in temperature than the first temperatureregion; boat means, removably inserted in the first temperature regionof the furnace means, for holding a plurality of wafers only in thefirst temperature region; temperature control means, including aplurality of temperature sensing elements arranged inside the furnacemeans, for maintaining a uniform temperature in the first temperatureregion; gas supply means for supplying a first reactive gas and a secondreactive gas into the second temperature region of the furnace means;and mixed gas supply means for mixing, in the second temperature region,the first reactive gas and the second reactive gas together and forsupplying the resultant mixed gas toward a portion of the plurality ofwafers in the first temperature region of the furnace means..Iaddend..Iadd.9. The semiconductor manufacturing apparatus according toclaim 8, wherein the plurality of temperature sensing elements arethermocouples. .Iaddend..Iadd.10. The semiconductor manufacturingapparatus according to claim 8, wherein the first and second gases reactto each other and are supplied toward the plurality of wafers to form afilm on the plurality of wafers. .Iaddend..Iadd.11. The semiconductormanufacturing apparatus according to claim 8, wherein the first andsecond gases are mixed together at a temperature suppressing pyrolysisof the first gas. .Iaddend..Iadd.12. The semiconductor manufacturingapparatus according to claim 8, wherein the mixed gas supply meansincludes a nozzle having a plurality of openings. .Iaddend..Iadd.13. Thesemiconductor manufacturing apparatus according to claim 8, wherein thefirst gas is dichlorosilane gas, and the second gas is ammonium gas..Iaddend..Iadd.14. The semiconductor manufacturing apparatus accordingto claim 13, wherein the ratio of the flow rate of the dichlorosilanegas to that of the ammonium gas is between 1:5 and 1:15..Iaddend..Iadd.15. The semiconductor manufacturing apparatus accordingto claim 13, wherein the temperature at which the dichlorosilane gas andthe ammonium gas are mixed together is between about 30° C. and about180° C. .Iaddend..Iadd.16. The semiconductor manufacturing apparatusaccording to claim 8, wherein the gas supply means separately suppliesthe first and second gases into the second temperature region of thefurnace means. .Iaddend..Iadd.17. The semiconductor manufacturingapparatus according to claim 8, wherein the gas supply means mixed thefirst and second gases together and supplies the resultant mixed gas tothe second temperature region of the furnace means. .Iaddend..Iadd.18. Asemiconductor manufacturing apparatus comprising:hot wall furnace meansincluding heating means for producing a first temperature region and asecond temperature region inside the furnace means, the secondtemperature region being lower in temperature than the first temperatureregion; boat means, removably inserted into the first temperature regionof the furnace means, for holding a plurality of wafers only in thefirst temperature region; temperature control means, heated by theheating means and including a plurality of temperature sensing elementsarranged inside the furnace means, for maintaining a uniform temperaturein a region surrounding the plurality of wafers; and mixed gas supplymeans for mixing, in the second temperature region, a first reactive gasand a second reactive gas together and for supplying the resultant mixedgas toward a portion of the plurality of wafers. .Iaddend..Iadd.19. Thesemiconductor manufacturing apparatus according to claim 18, wherein theplurality of temperature sensing elements are thermocouples..Iaddend..Iadd.20. The semiconductor manufacturing apparatus accordingto claim 18, wherein the first and second gases react to each other andare supplied toward the plurality of wafers to form a film on theplurality of wafers. .Iaddend..Iadd.21. The semiconductor manufacturingapparatus according to claim 18, wherein the second gas serves to retardpyrolysis of the first gas. .Iaddend..Iadd.22. The semiconductormanufacturing apparatus according to claim 18, wherein the first andsecond gases are mixed together at a temperature which suppressespyrolysis of the first gas. .Iaddend..Iadd.23. The semiconductormanufacturing apparatus according to claim 18, wherein the mixed gassupply means includes a nozzle having a plurality of openings..Iaddend..Iadd.24. The semiconductor manufacturing apparatus accordingto claim 18, wherein the first gas is dichlorosilane gas, and the secondgas is ammonium gas. .Iaddend..Iadd.25. The semiconductor manufacturingapparatus according to claim 24, wherein the ratio of the flow rate ofthe dichlorosilane gas to that of the ammonium gas is between 1:5 and1:15. .Iaddend..Iadd.26. The semiconductor manufacturing apparatusaccording to claim 24, wherein the temperature at which thedichlorosilane gas and the ammonium gas are mixed together is betweenabout 30° C. and about 180° C. .Iaddend..Iadd.27. A semiconductormanufacturing method for use in a semiconductor manufacturing apparatuscomprising: a hot wall furnace having a gas introducing port, a gasexhaust port, and a heater; a boat inserted into the furnace and capableof holding a plurality of wafers; and temperature control means insidethe furnace, the semiconductor manufacturing method comprising the stepsof:causing the temperature control means to control the heater tomaintain a first temperature region surrounding the plurality of wafersat a uniform temperature sufficiently high to perform wafer processing;mixing a first reactive gas and a second reactive gas together in asecond temperature region inside the furnace at a temperature lower thanthe first temperature region so as to obtain a mixed gas, said first andsecond reactive gases reacting with each other to form the mixed gas;and supplying the mixed gas toward the plurality of wafers in the firsttemperature region such that the mixed gas reaches at least the vicinityof the plurality of wafers. .Iaddend..Iadd.28. The semiconductormanufacturing method according to claim 27, wherein the first gas isdichlorosilane gas, and the second gas is ammonium gas..Iaddend..Iadd.29. The semiconductor manufacturing method according toclaim 28, wherein the dichlorosilane gas before mixing is maintained ata temperature within a range of between about 30° C. and about 180° C..Iaddend..Iadd.30. The semiconductor manufacturing method according toclaim 28, wherein the ratio of the flow rate of the dichlorosilane gasto that of the ammonium gas is between 1:5 and 1:15. .Iaddend..Iadd.31.The semiconductor manufacturing method according to claim 27, whereinthe mixing step is performed using a nozzle having a plurality ofopenings. .Iaddend.